The present invention relates generally to electric traction systems and more specifically to the use of energy batteries and power batteries in combination for producing tractive effort and for non-traction purposes. While this disclosure emphasizes the use of electric traction systems in locomotives and off-highway vehicles, it will be obvious to one of ordinary skill in the art that the instant invention is useful in other vehicular and non-vehicular applications as well.
In a wide variety of applications, electric traction systems include electric batteries to improve system efficiency. These batteries are typically classified as either “energy batteries” or “power batteries” depending on whether their designs are optimized for energy density or power density, respectively. Some traction applications favor one battery class over the other; other applications favor a combination of both energy and power batteries. During motoring operation, the batteries are discharged through electric motors to produce tractive effort. During braking operation, the motors are operated as generators to re-charge the batteries.
In systems incorporating both energy and power batteries (dual battery systems), initial and supplemental charging of the energy batteries are typically achieved either mechanically, by replacing parts of the battery, or electrically by coupling to the power utility grid. An opportunity exists, to provide an alternative means of charging energy batteries in dual battery systems.
In addition to providing power for the traction application, the traction system's electrical power production capability can be used for non-traction purposes. Additional opportunities exist, therefore, to exploit the electrical power production capability of electric traction systems for non-traction applications.